In many different industries, microorganism contamination can be a significant problem. For example, in the food service industry, food products are often prepared on hard surfaces such as counters, tables, and the like. Microbes (e.g., viruses, bacteria, fungi, and the like) from these products can collect on the surfaces, and later transfer to a cleaning cloth, towel, or wipe that is used to clean the surfaces. After transfer, the microbes can remain on the cloth, towel, or wipe and begin to grow in population due to the favorable environment often provided by such materials. Thus, such microbes can actually cross-contaminate other environments, such as additional surfaces, the hands or skin of a user, etc., when contacted therewith.
In an attempt to prevent such surface and cloth contamination, wipers containing certain antimicrobial agents have been employed. For instance, many of these antimicrobial wipers are impregnated with antimicrobial agents that are delivered to the user in a premoistened form. However, the disinfecting agent within the wiper is readily exhausted after a short period of time. Thus, such premoistened wipers either only mildly inhibit growth on the wipers and/or the hard surfaces cleaned or may only be used for a very limited number of wipes.
Other types of wipers have also been developed to provide antimicrobial activity. For example, one such wiper is described in U.S. Pat. No. 4,929,498 to Suskind, et al. In particular, the wiper described in Suskind, et al. is formed from a nonwoven fabric that contains fibers and an antimicrobial agent (preferably an organosilicon quaternary ammonium salt) distributed on 10% through 50% of the fibers. The antimicrobial agent is said to be substantive to the fibers so that it is substantially prevented from diffusing therefrom. However, although such wipers may overcome the problems of conventional premoistened wipers in which the antimicrobial agent is readily exhausted, such wipers still tend to provide inadequate microbial kill percentage.
Another conventional wiper, known as the xe2x80x9cKeri Kleanxe2x80x9d food service wiper, is formed from rayon and polyester fibers in a dry lay carding process. The fibers are then subjected to hydroentanglement and then saturated in a bath that contains an antimicrobial agent. After being applied with the antimicrobial agent, liquid is squeezed from the nonwoven material, which is then dried. However, one problem with such a method is that, in order to xe2x80x9cdip and squeezexe2x80x9d the nonwoven into an antimicrobial bath, additional equipment may be required. Such additional equipment can decrease the efficiency of the process, as well as increase costs.
As such, a need currently exists for a more effective method of forming an antimicrobial nonwoven product, such as a cloth, towel, or wipe.
In accordance with one embodiment of the present invention, a method for forming an antimicrobially-treated fabric is provided that includes forming a solution from a liquid and an antimicrobial agent. In general, any of a variety of antimicrobial agents can be used in the present invention. For example, in some embodiments, the antimicrobial agent is an organosilicone quaternary ammonium compound. One suitable organosilicone quaternary ammonium compound that can be used in the present invention has the following structure: 
wherein,
R1 is hydrogen or a C1-C8 alkyl group;
R2 is hydrogen or a Cl-C8 alkyl group;
R3 and R4 are the same or different, and are selected from the group consisting of hydrogen and a C1-C4 alkyl group;
R5 is hydrogen or a C1-C30 alkyl group; and
Xxe2x88x92 is a suitable counterion.
For example, in one embodiment, the antimicrobial agent is 3-(trimethoxysilyl)propyloctadecyidimethyl ammonium chloride.
A cellulosic fibrous material is combined with the solution to form a liquid suspension in which the antimicrobial agent becomes substantive to the cellulosic fibrous material after being combined therewith. The antimicrobial agent can be present within the solution in an amount up to about 5% by weight of the treated fibrous material, in some embodiments between about 0.04% to about 1.0% by weight of the treated fibrous material, and in some embodiments, between about 0.2% to about 0.5% by weight of the treated fibrous material. In some embodiments, the cellulosic fibrous material and antimicrobial solution are combined in a pulper. The materials may also be subjected to agitation, if desired, to improve the likelihood that substantially all of the antimicrobial agent will become substantive to the cellulosic fibrous material.
The liquid suspension is then formed into a web using any of a variety of techniques such that substantially all of the cellulosic fibrous material present within the web is derived from the antimicrobially-treated cellulosic fibrous material. In some embodiments, the web of antimicrobially-treated fibrous material may also be hydraulically entangled with a nonwoven substrate. The nonwoven substrate may be formed from continuous filaments, such as those formed by a spunbond process. In some embodiments, the web of antimicrobially-treated fibrous material is then dried so that the antimicrobial agent forms a covalent bond with the cellulosic fibrous material.
In some embodiments, during formation of the fabric, such as described above, at least a portion of the liquid is removed from the liquid suspension. Such removal can be accomplished in a variety of different ways, such as through the use of gravity, vacuum boxes or shoes, dryers, and the like. However, regardless of the mechanism used to remove the liquid, the portion of the liquid that is removed is substantially free from the antimicrobial agent. Accordingly, such liquid may sometimes be recycled or disposed of without requiring additional mechanical or chemical treatment.
Other features and aspects of the present invention are discussed in greater detail below.